According to police, a witness saw her put a substance into several of the children’s cups on Friday, and Gratz later acknowledged she had laced the cups with an over-the-counter sleeping aid.

None of the children drank from the cups.

Sgt. Troy Hoefling says investigators are trying to determine whether Gratz had used the sleeping aids before. He says her motive is under investigation. Police believe the alleged incident happened before a scheduled nap.

Gratz was being held Tuesday without bail. Hoefling said he did not think she had secured an attorney.